Comments follow in the order in which they were received.
1. From Sheldon Stone
(received July 8)
Thank you very much for this excellent report. One general comment
is that since this was based on a previous report from two years ago
before LHCb started running their tends be a asymmetry between the
comments related to the success of e+e- B factories and the success
of LHCb. I will suggest some changes for your consideration.
Line
110 After "The B factories" please add "and LHCb" so the
sentence reads "The B factories and LHCb provided many stringent
tests by precisely measuring numerous CP-violating
and CP-conserving quantities ..."
162 Specify B0-antiB0, because this doesn't apply to Bs.
165 Add a sentence for Bs such as: " A similar conclusion
exists for the Bs system based on LHCb measurements." Then modify
next sentence to be specific to kaons and Delta F=1 processes.
189 change to "BARBAR, BELLE, and LHCb"
207 I don't understand the phrase "inclusive B decays" here
Table 1-2 caption- What does "parametric" mean?
270 Perhaps put the word "theoretical" before "branching"
289 "dimensionful" is not an English word, perhaps
"dimensional"?
457 Change "super flavor factor" to "experiments"
473 Remove the word "The" in front of LHCb
527 The sentence on quantum correlation is misleading. You can
tag without quantum correlated B's. Perhaps "Detection of the
decay products of the other B allows the decay of one B to tag the
flavor of the other."
536 This bullet has proven true only for B+ and B0
decays. While this has been proven to be quite useful for everyone
does it deserve a bullet particularly in terms of future
measurements?
606 A calculation indicates that the LHCb sensitivity to
the Ds*Ds* and Ds*rho modes may be conquerable to that of a e+e-
machine, since LHCb does have photon detection and the numbers of
produced Bs events are so much higher. In fact, these decays can
be observed in some cases without the photon reconstruction since
these channels appear at somewhat lower B masses than the DsDs and
Dspi peaks.
629 Suggest making the introductory sentence here the same as
line 522 which says "The spectacular successes of the B-factory
experiments Belle and BABAR highlight the advantages
of e+e− collider experiments:"
Specifically change the sentence to
"The spectacular successes of LHCb have realized some of the great
potential for studying the decays of particles containing
charm and bottom quarks at hadron colliders."
645 I suggest a new paragraph here that says something
like "The key elements for reducing backgrounds are the ability to
accurately form a detached
vertex for b or c hadron
decays, and the ability to identify particles. Once heavy hadron
decays are isolated from the primary vertex multiple mass
combinations from the
underlying event are no longer a concern. The particle
identification severely reduces the backgrounds from similar
modes
with similar topologies but
different particles. Triggering has been shown to be at least 50%
efficient on most modes of interest involving hadronic
decays, with efficiencies
approaching 90% for decays involving dimuons."
2. From Doug Bryman (received
July 8)
39 Nevertheless,
before looking forward, it provides useful context to
briefly review a history of missed opportunities
in which the US program ceded leadership to overseas
efforts.
41 ... The most
42 sensitive rare K decay experiments
performed to date were then underway at the Brookhaven AGS
including discovery of the ultra-rare K+->pi+ nu nubar
decay,
, and observation of direct CP
violation in K0->2 pi decays in a fixed-target
experiment using the Tevatron at
44 Fermilab.
46 ... door to measurements of time-dependent CP
asymmetries. (redundant mention of 2008 Nobel
prize line 102 -- one is enough)
59 Motivated by strong physics imperatives, a
rich heavy-quark flavor physics program is flourishing
around
61 construction in Japan and
Europe. Indeed, CERN | the laboratory that now owns the
Energy Frontier |
62 ...and a rare K
63 decay program (NA62) focusing on K+->pi+
nu nubar which will begin taking data in parallel with
LHC running in 2014. This
reflects...
81 the energies accessible ...
98 quark mass [5, 6] before charm particles were directly
detected. The larger than expected...
109 since the 1960s, precision tests of the CKM picture of
CP violation in the kaon sector were initially
hindered ...
179 3. What can be expected in terms of experimental
precision and which processes provide the
greatest leverage for discovery of BSM physics?
259 In the arena of kaon decays, a key role is played by the
FCNC modes mediated by the quark-level processes
260 s ! d(; `+`�; ), and in particular the
theoretically cleanest modes K+ ! + KL !
0. Other processes of great interest include
....
OMIT:
353 Following U.S. termination of a world-class kaon
program by 2002, leadership in kaon physics shifted to
354 Europe and Japan.
New:
353 An extensive program of kaon decay experiments aiming
for orders of magnitude improvements in reach for new
physics is flourishing worldwide.
357 2014. The NA62 goal is to measure the K+ ! +
branching ratio with O(100) events (10% precision) ...
3. From Roger Forty (received
July 10)
I
agree with the comments that Sheldon already
sent. In addition, the phrasing around
line 671 seemed rather negative to me, one could point
out that we limit
our luminosity for good reasons (reducing pile-up, and
dose in the forward
region) but still achieve enormous yields.
Otherwise, some typos I spotted:
Line 18: discusses -> discusses the
Table 1-1: still has ?? next to some entries
Line 173: magnitudes -> magnitude
Line 879: n -> in
Line 885 "which are express" needs rephrasing
Line 914: the word "observation" should be
avoided for Bs -> mumu, perhaps
"measurement"
Line 935: related -> relate
Line 946: sever -> serve
Line 959: payed -> paid
Line 1332: committments -> commitments
4. From Monika Blanke (received July 11)
First of all I would like to thank everyone who contributed to
the excellent writeup of this report. It is very well written and
exhaustive. I have a few remarks:
l.18 discusses the experimental program
l.77 and regain some of its
Table 1-1 In the last two rows there are some question marks
Figure 1-1 still needs to be updated (just a reminder)
l.269 There is a huge space after "see Ref. [16]"
l.275 currently dominated by the uncertainty in
CKM parameters
l.335 The possible distinction between LH and RH currents in
K_L -> mu mu and K -> pi nu nu has previously been discussed
in [31] and
http://arxiv.org/abs/0906.5454.
l.353 Following the U.S. termination
l.461 This sentence is rather confusing. I would reformulate it
as:
Observables that are especially interesting for the
future $B$ physics program are the ones that…
l.465 and 468
the "l" in the formulae should be an "\ell"
l.490 The comparison between exp. result and SM prediction is
misleading, as these are not for the same quantity. The SM value
quoted here is for the flavor tagged decay, while the LHCb result
is time-integrated and uses no flavor tagging. See [45].
The smae applies to l.702-704.
l.505 "In the SM" at the beginning of the sentence should be
removed.
l.631 "per second" should be removed (that's already contained
in kHz)
l.701 I would remove the first sentence, as
a) it states the obvious
b) already the previous paragraph discusses LHCb results
l.715 the most precise so far, and are in good
agreement
l.716 sensitive to NP have also been
l.742 charm quarks
l.747 complimenting -> complementing
l.755 complimentary -> complementary
l.783 complimentary -> complementary
l.823 I don't understand the mentioning of W_R in this context
- it still suffers from the helicity suppression mentioned in the
previous sentence.
l.842 relied on the time-dependence
l.848 over the next several years
l.855-856 I don't understand the last sentence of this
paragraph. Since we do not know the sign of the SM contribution,
we do not know whether there is constructive or destructive
interference. Hence I think the only reliable constraint is on NP
contributions whose absolute value is significantly larger than
any reasonable estimate for the SM contribution.
section starting in l.857
There are three different conventions here for writing CP
violation (with or without hyphen, CP vs. $CP$). It would be nice
to stick to one (consistent with the rest of the report).
(1.13) strictly speaking the bounds are on the absolute values
of ImC
l.935 strong phases are needed to relate observables
l.980 decays constants -> decay constants
l.1071 G-parity boundary conditions
l.1072 for the past three years
l.1248,1263,1275 B-physics -> $B$-physics
l.1264 an HEP -> a HEP
l.1334 breath -> breadth
5. From Ruth Van de Water (received July
13)
Thank you very much for all of
your obvious hard work on this document. It makes a
very strong case for a vigorous US flavor-physics program.
I therefore have no major
comments on the content, and only a few hopefully
easy-to-implement wording suggestions which I list below:
1) Lines 197-200
197 Nonperturbative effects
arise because QCD becomes strongly interacting at low
198 energies. These are often the limiting uncertainties,
since, in general, there is no systematic method to
199 calculate them model independently. There are,
nevertheless, several possibilities to get at the
fundamental
200 physics in certain cases, even in the presence of such
uncalculable effects.
I think that the statement that there is "no systematic
method" to calculate nonperturbative QCD effects model
independently, and later that they are "uncalculable" is too
strong. I would simply remove these statements, because
I don't think they're necessary, and say something like:
"Nonperturbative effects
arise because QCD becomes strongly interacting at low
energies. There are several possibilities to get at the
fundamental physics in certain cases:"
Then, later on in the last lattice-QCD bullet, I would
change "robust" --> "precise".
2) Lines 241-243
214 Lattice QCD allows in
principle model independent calculations of nonperturbative
242 phenomena. In practice, approximations have to be
used to keep the computational time under control, e.g.,
243 because the b quark is too heavy to be simulated
directly.
Here I think that the underlying important point is that the
precision of lattice-QCD calculations is often limited by
systematic uncertainties. So I would instead say
something like:
"Lattice QCD allows first-principles calculations of
nonperturbative phenomena. In practice, the numerical
simulation parameters such as pion masses, lattice spacings,
and spatial volumes, are constrained by limited computing
resources. These introduce systematic uncertainties that
can be studied directly by simulating lattices with different
parameter sets and/or estimated using effective field theory."
3) Line 468:
468 present theory error on
jVubj from exclusive B ! l can be reduced from present 8:7%
to 2% by 2018 [41].
In addition to citing Ref. [41], you can cross-reference Table
1-6 in the LQCD section of the report.
4) Lines 847-849:
847 Theoretical predictions for
x and y in the SM are uncertain, although values about 1%
had been expected [95].
848 The predictions need to be improved over next several
years. Several groups are working to understand the
849 problem using technology of heavy quark expansion and
other long-distance methods, including lattice QCD.
I would reword the last sentence to make it more clear that
lattice-QCD is one of the technologies:
"Several groups are working to understand the problem using
technology such as the heavy-quark expansion, lattice QCD, and
other long-distance methods."
5) Lines 1346 -- 1349:
1346 Back-and-forth between
theory and experiment is necessary for progress in
quark-favor physics, as in
1347 any field of physics. Therefore, stable support for
theorists working in this area is essential. Lattice
1348 QCD also plays a critical role, and support for the
computing facilities needed for LQCD progress
1349 should be maintained.
This statement is great! I would just remove the word
"also" in the last sentence, since we're theorists too.
;)
6. From Norman Christ (received July 16)
The report is surely strong and well-done! A minor
technical issue which should be brought up to date
is a now too restrictive statement about the sorts
of states that lattice methods can reliably treat.
You might consider the following substitution for
the third bullet in lines 208-210:
"208 Lattice QCD is a model independent method to address
nonperturbative
phenomena. In practice, the
209 most robust results are for matrix elements
involving at most one
hadron in the initial and the final
210 state (allowing, e.g., extractions of magnitudes of
CKM elements)."
-->
Lattice QCD is a model independent method to address nonperturbative
phenomena. In practice, the most robust results are for matrix
elements
involving one or at most two hadrons in the initial and the final
state
(allowing, e.g., extractions of magnitudes of CKM elements).
As described elsewhere in the report, lattice methods now
give reliable predictions for pi-pi or pi-K scattering for
energies below 3- or 4-particle thresholds and for decays
such as K->pipi, again neglecting the highly suppressed
3-particle channels. Thanks!
7. From Jonathan Rosner (received July 17)
COMMENTS ON
REPORT OF THE QUARK FLAVOR PHYSICS WORKING GROUP
J. ROSNER - JULY 17, 2013
General comments
----------------
This is an excellent writeup. There are a few places where one
need not go
into so much detail, but on the whole the balance is good and the
concluding
section ("A U. S. Plan ...") is appropriately crisp.
A Table of Contents and a Glossary of acronyms would be
helpful. I have
asked the neutrino subgroup to provide this as well.
A six-page Executive Summary is needed, with quotable
figure(s)/table(s),
to provide input to Conveners' writeups.
Author list: [removed]'s name is misspelled. Check
spellings of
other names.
Optional: In the Introduction, highlight the mystery of quark
and lepton
masses and mixings - does the pattern stem from physics at a deeper
level?
"data set" is two words
One sees "sizeable" in some places and "sizable" in others.
Decide which.
"parametrize(d)" (no second "e") is the preferred US spelling.
"model-(in)dependent" : hyphenate the compound adjective
Make sure you use the symbol $J/\psi$, not $\psi$, for the meson
The "D0 Collaboration" (D-zero), not "DO Collaboration"
The B meson should be written in math mode: "$B$"
Capitalize only first words of headings and subheadings
Prefer no capitals on "new physics" (OK for "NP" acronym) or
"quantum chromodynamics" (OK for "QCD" acronym)
Migrate as many references as possible to arXiv
Nucl. Phys. B references (e.g., [22]) {\bf B546}, 299 (1999)
(bold face letter not separated from bold face volume number)
JHEP references: use PRD style, "J. High Energy Phys. mm (yyyy)
aaa,"
where mm stands for month (no bold face), yyyy for year, and aaa for
article number.
Line-by-line comments:
---------------------
L18 "discusses the experimental program"
L26 "has not changed" (except for the Higgs discovery, which
provides
some focus - see L120-123)
L67 "distinguish between" => "distinguish among" (more than
two models)
L85 "direct" => "indirect" ?
L98 "larger-than-expected" (hyphens)
P4 Table 1-1 What do the "??" mean on the last two
lines? Numbers still
to be checked? Check them, delete "??", or explain in the
caption
L162 "[12,9]" => "[9,12]"
L173 "magnitude"
L214 "measurements"
L216 "consider"
L218 "decay modes"
P8 Table 1-2 Explain facilities, e.g., in an Appendix with
definitions
of acronyms and experiments
L267 "observables, " (comma)
L281 "CP-violating" (hyphenate compound adjective)
L292 "of" not needed
L300 and following paragraph Can this be simplified and
shortened? Can
one explain briefly in words why $\epsilon'_K/\epsilon_K$ provides
the
strongest constraint? Try to distill the essence of L300-335
and say it
in less technical terms.
L337 "[20,31]"
L338 "between" => "among" if > 2
L377 "high-precision" (hyphenate compound adjective)
L403 "the RSVP (...) project"
L406 "low-momentum" (hyphenate compound adjective)
L414-418 What about neutron background?
L469 "are even smaller"
L472 "one-loop" (hyphenate compound adjective)
L472 "are below"
L474 "statistics-limited" (hyphenate compound adjective)
L475 "loop-induced" (hyphenate compound adjective)
L476 "time-dependent" (hyphenate compound adjective)
L476 Delete comma after "modes"
L484 "penguin-dominated" (hyphenate compound adjective)
L485 "tree-dominated" (hyphenate compound adjective)
L489 "$(\tan \beta)^6$-enhanced" (hyphenate compound
adjective)
L510-515 Are we still waiting for the Belle result on $B \to
D^{(*)}
\tau \nu$?
L520 Should $\mu \to e$ conversion and $\mu \to e \gamma$ be
mentioned?
L524-525 "quantum-correlated" (hyphenate compound adjective)
L525 "allows"
P17 Table 1-3 Not clear what is given in the column "SM theory
uncertainty"
L563 "done" => "measured"
L664 "provide $K-\pi$ separation" - by how many $\sigma$ ?
L699 "therefore" => "so"
L701-704 Repeats some of L489-...
P22 Table 1-4 Explain "$s_0$ (lower left) in caption
L722 "during the present and upgraded phases of the LHCb
experiment"
L752 "and can also help"
L760 "$D$ mesons" (no hyphen)
L781 "[51,88]"
L781 "the data are unique in their ability"
L782 "excel"
L783 "complementary"
L804 "This" => "The"
L817 "isospin-related" (hyphenate compound adjective)
L841 Delete comma after "parameters"
L842 "high statistics" (no hyphen)
L847 "about 1\%" => "as high as $\sim$ 1\%" (many authors
published less)
L856 "as observed experimentally": but $x \ne 0$ hasn't
been established
L857-883 Candidate for reduction of length - can the bootom
line be
explained in words?
L876 "DCSD" - defined previously?
L877 Note that at equal decay times, like-sign $K^\pm \pi^\mp$
decays are
forbidden by Bose statistics. See, e.g., Phys. Rev. D35 (1987)
2166.
P27 Table 1-5 caption L2 Was "$\lambda_{K^+K^-}$" defined
previously?
L885 Delete "are"
L889 "CP violation" (no hyphen)
P27 Eq. (1.12) Quoting just this result gives a misleading
impression.
Is it more trustworthy than all the others which suggest an opposite
sign?
L906 "provide a better handle"
L910-911 If shortening P26, shorten this correspondingly
L913-930 These decays are a long shot - could shorten this
subsection
L935 "related" => "relate"
L938 "Recent observations" (to go with "are")
L942 "Experimental data continue"
L946 "These results serve"
L959 "payed" => "paid"
L966 "quark" => "quarks"
L994-... Good but can it be condensed a bit?
L1043-1044 I think you have K_S and K_L interchanged
L1060 "15-year" (hyphenate compound adjective)
L1061 Here is where one might consider condensing (keeping all
references).
Not all the details are necessary (especially in L1082-1099)
L1117,1118-1119 "CP violation" (no hyphen)
L1121-1132 This is good - don't cut
L1133 "four-particle" (hyphenate compound adjective)
L1146 "presently" => "currently"
L1153 "form factors" (no hyphen)
L1189-1242 Good but could say in fewer words
L1249-1251 Don't comment on other people's troubles
L1271-1273 Good - stressing synergy
L1290 "constrained"
L1294-1299 Excellent - make sure these points make it into the
final
Convener's report.
L1334 "breadth"
L1356 {\bf 18} in two places
L1363 {\bf 56}, 501 (2006)
L1383, 1385 Letter not bold and spaced from volume number
L1461 "R. Aaij"
8. From Michael Kohl (received July 18)
I am speaking for TREK.
I suggest to add the following sentence in line 370 before "The
uncertainty":
"At the same time, this measurement allows for sensitive searches
of a heavy sterile neutrino ($N$) in $K^+ \to \mu^+ N$, and for
light
bosons (heavy photons from the dark sector, $A' \to e^+ e^-$) in the
$K^+ \to \mu^+ \nu_mu e^+ e^-$ and $K^+ \to \pi^+ e^+ e^-$ decays,
where
the new particles would be identified as narrow peaks in the
respective
momentum and ($e^+ e^-$) invariant mass spectra."
9. From Gil Paz (received July 21)
This is a very well written report. I have several specific
comments, mainly about the wording. I list them in the order in
which they appear.
Line 52: "predilection": The sentence loses its momentum by
the use of this somewhat obscure word, "tendency" would be a better
choice.
Line 61: "Indeed" -> "For example"
Line 64: Add "the U.S. must be a part of this effort" at the end of
the sentence.
Line 65-72: Flavor physics can, as it has done in the past, imply
the existence of new states. For example, imagine a whole set of new
particles, where only the lowest lying states are seen at the LHC.
Constraints from flavor physics can tell us what should be the mass
of the missing states.
Line 84: "t-s, d" -> "top-strange and top-down quarks"
Line 117: "SM flavor structure is very special": compared to
what? We know about the quark and lepton flavor structure and not
more. Are we assuming some "probability distribution" for the Yukawa
coupling? I would just drop the expression.
Line 124: Add "possibly" between "except" and "for"
Line 207: "and to estimate them" -> "and to extract them
from data or estimate them"
Line 237-238: After "it is the analysis of subleading effects
where many of the theoretical challenges lie." add "The theoretical
tools that can address these issues (HQET, SCET etc.) are
well-developed and can be readily applied when new experimental data
becomes available."
Line 269: delete space after "Ref [16]".
Line 357: add the number of events sensitivity after 10%.
Line 469: Reference table 1-6.
Line 516-518: The sentence is too long. Perhaps it can be
simplified.
Table 1-3: "SM theory uncertainty" -> "SM theory
uncertainty/prediction"
Line 876: Define "DCSD".
Line 888-897: "Thus" appears both in line 894 and in line 896.
Line 959: "should one be built abroad." One could also mention the
possibility of US charm experiment...
Line 1247-1249: "It is very difficult to foresee a scenario that
leads to the construction of a facility in the U.S. that is capable
of supporting B-physics or charm-physics experiments." How about we
suggest such a scenario?
Line 1254: "dodo bird": It's a nice metaphor but might be too
pessimistic. I would avoid this expression.
Line 1255: "whether and how the U.S. should pursue
research in quark-flavor physics." I would say "how can the U.S.
regain leadership in quark-flavor physics"
Line 1264: Drop "predictably difficult budgets will impose
limitations," nothing is gained from saying this.
Line 1290: Drop "Of course, with constrainted funding, this
opportunity must be weighed against others outside the subject area
of this working group." nothing is gained from saying this.
Line 1315-1316: Drop the space between the lines.
Line 1349: Add an ending line with an optimistic note?
10. From Alexey Petrov (received
July 22)
1. It might be
important to emphasize that b-quark physics would not be
bounded by decays (or mixings) of B-mesons only. In principle,
decays of B_c mesons as we as b-flavored baryons are important
for the Intensity Frontier. On the experimental side the data
would eventually simply be there, while on theoretical side
the QCD-related uncertainties are clearly different from the
ones in B-meson decays. The report barely mentions heavy
baryons and does not mention B_c mesons, while methods to
extract CP-violating
asymmetries have been proposed for both system.
At this stage I'd propose to add/change a couple of sentences:
1a. Line 28: change "B-physics" to "beauty"
1b. Line 449: change "B-physics" to "b-quark physics"
1c. After line 520: add "It is also important to explore
possible use of $B_c$ and b-flavored baryons for studies of
CP-violating parameters. Decays of these particles could be
useful due to different systematic errors and theoretical
methods from the ones
discussed above."
2. Line 207: change period to comma and add "or obtain them
from other experimental data" (like matrix elements of
chromomagnetic operator)
3. Line 236: before sentence "As is often..." add "In
addition, large $N_c$ limit sometimes allows to obtain
relations among some nonperturbative parameters.
I also believe that the sentence mentioning the dodo bird is
way too pessimistic...